Question

I only want to remove resources if they actually belong to the object. For example:

Post.all.each do |post|
    if post.has_method?('name')
        true
    else
        false
    end
end

But checking for an association:

Post.all.each do |post|
    if post.has_many?('tags')
        true
    else
        false
    end
end

or:

Post.all.each do |post|
    if post.belongs_to?('category')
        true
    else
        false
    end
end

Answer 1

you can write your own methods:

def has_many?(association)
  self.class.reflect_on_all_associations(:has_many).any?{|a| a.name == association}
end

def belongs_to?(association)
  self.class.reflect_on_all_associations(:belongs_to).any?{|a| a.name == association}
end

so

Post.all.each do |post|
  post.has_many?('tags') ? "yeap" : "nope"
  post.belongs_to?('category') ? "yeap" : "nope"
end

Or you can use simple construction:

Post.all.each do |post|
  post.methods.include?('tags') ? true :false
  post.methods.include?('category') ? true :false
  post.methods.include?('name') ? true :false
end

UPD

Or, as you correctly pointed, you can use respond_to?

 post.respond_to? :comments